In recent years, minimization has quickly progressed as a result of the development of lithographic techniques in the field of fine processing for production of semiconductor elements or liquid crystal elements. As such means for the minimization, generally, the wavelength of irradiation light has been shortened. Specifically, such irradiation light has been changed from the conventional ultraviolet ray including g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm) as typical examples, to DUV (Deep Ultra Violet) of shorter wavelengths.
At present, a KrF excimer laser (wavelength: 248 nm) lithographic technique has been introduced into the market, and an ArF excimer laser (wavelength: 193 nm) lithographic technique and an F2 excimer laser (wavelength: 157 nm) lithographic technique, which are directed towards further shortening the wavelength, are being studied. Furthermore, recently, immersion lithographic techniques thereof are being studied. Moreover, an electron beam lithographic technique, which somewhat differs from the above techniques, is also being intensively studied.
As a resist with high resolution for such irradiation light of a short wavelength or electron beams, a “chemically amplified resist” containing a photoacid generator has been proposed. At present, the improvement and development of this chemically amplified resist have been progressing.
For example, as a chemically amplified resist resin used in the ArF excimer laser lithography, an acrylic resin that is transparent to light of a wavelength of 193 nm has become a focus of attention. As such an acrylic resin, for example, a polymer of (meth)acrylate having an adamantane skeleton at an ester moiety thereof and (meth)acrylate having a lactone skeleton at an ester moiety thereof is disclosed in Patent Document 1, Patent Document 2, and the like.
However, when these acrylic resins are used as resist resins, at the time of development processing by means of an alkali developer for producing resist patterns, defect of development which is referred to as a “defect” may occur. Due to this defect, voids appear in a resist pattern, and as a result, disconnection or defect of a circuit may occur and the yield of the production process of semiconductors may be decreased. These polymers are produced without using a chain transfer agent such as thiols, causing a problem of broad molecular weight distribution.
Patent Document 3 discloses a resin having a carboxylic acid group on at least one terminal of its molecular chain and having the solubility to an alkali developer increased by the action of an acid. However, in the resist composition containing the resin, during storage of the resist composition, a carboxylic acid at the molecular terminal may cause an elimination reaction of functional groups which become alkali-soluble by an acid, the resist performance such as a change in the sensitivity may be deteriorated.
Patent Document 4 discloses a resin containing constituent units having adamanthyl skeletons and constituent units having lactone skeletons, and having a velocity of dissolution in an alkali developer increased by the action of an acid, wherein at least one terminal of its molecular chain is a specific group such as a thiohydroxy group and a thiocarboxy group derived from a sulfur-containing chain transfer agent.
Since such resins are produced using a sulfur-containing chain transfer agent, the molecular weight distribution is narrow. However, while being stored, decomposition of a photoacid generator may be promoted, the resist performance such as a change in the sensitivity may be deteriorated.
Meanwhile, Patent Document 5 discloses a method for manufacturing a polymeric compound for a photoresist containing constituent units having adamanthyl skeletons and constituent units having lactone skeletons, and having a velocity of dissolution in an alkali changed by the action of an acid, wherein polymerization is performed using one or more solvents such as propylene glycol monomethyl ether acetate (hereunder, referred to as PGMEA) and a mixed solvent of propylene glycol monomethyl ether/PGMEA, as a polymerization solvent.
However, a resin obtained by the method for manufacturing a polymeric compound for a photoresist has a superior solubility in a resist solvent but a small number of hydrophilic terminals, and thus a poor compatibility into an alkali developer and a broad molecular weight distribution. Therefore, as well as Patent Document 1 and Patent Document 2, voids appear in a resist pattern due to a defect, and as a result, disconnection or defect of a circuit may occur and the yield of the production process of semiconductors may be decreased.
Furthermore, when a resist polymer containing a constituent unit having a hydrophilic group is to be produced, if reprecipitation is performed using PGMEA as a polymerization solvent, and methanol or a mixed solvent of ethanol/water as a poor solvent, then the precipitated polymer may become a sticky substance, the polymer may be unable to smoothly pass through the production process of polymers.    Patent Document 1: Japanese Unexamined Patent Application, First Publication H 10-319595    Patent Document 2: Japanese Unexamined Patent Application, First Publication H 10-274852    Patent Document 3: Japanese Unexamined Patent Application, First Publication H 10-55069    Patent Document 4: Japanese Unexamined Patent Application, First Publication 2001-117232    Patent Document 5: Japanese Unexamined Patent Application, First Publication 2003-206315